Gene and chromosomal mutations

Question 1

Mutations are…

They can occur in … or …

Answer 1

a random change in the DNA base sequence of an organism

genes or chromosomes

Question 2

types of chromosomal mutations (4)

Answer 2

insertion, deletion, duplication, translocation

Question 3

Some reasons for mutations:

Answer 3

viruses
irradiation
mutagens (chemical assaults)
DNA replication errors

Question 4

can mutations be inherited?

Answer 4

yes

Question 5

the body can correct DNA replication errors via…

Answer 5

base excision repair mechanisms - removing helix distorting base pairs

Question 6

polymorphisms?

Answer 6

normal DNA variations that are common in the population (unlike mutations)

Question 7

Point mutations

Answer 7

usually occur during DNA replication or transcription

this is mutations in the nucleotides that make up our genes as DNA and RNA polymerase make errors.

Question 8

Types of point mutations (3)

Answer 8

Insertion, deletion, substitution

Question 9

silent mutations?

Answer 9

mutation still produces the same protein sequence

as the triplet codons are degenerate

Question 10

Missense mutation

Answer 10

change in RNA, triplet codon and different amino acid
(sickle cell anaemia)

Question 11

Nonsense mutation

Answer 11

mutation leads to a stop codon

Question 12

Frameshift mutation

Answer 12

caused by insertion or deletetion
Insertion = right, deletion = left

Question 13

Aneuploidy

Answer 13

numerical abnormalities where there is a loss or gain of chromosomes.

leads to the incorrect no. of chromosomes (46)

Can involve autosomes and allosomes

Question 14

Why does aneuploidy occur?

Answer 14

due to non-disjunction (failure to separate during meiosis)

Question 15

What does aneuploidy lead to (3)

Answer 15

monosomy (loss of one)

trisomy (loss of one)

tetrasomy (4 copies of a chromosome instead of 2)

Question 16

Structural abnormalities with chromosomes (6)

Answer 16

duplication
inversion
deletion
insertion
translocation
ring chromosome

Question 17

Duplication?

Answer 17

part of a chromosome is copied
increased gene expression of this

Question 18

Inversion

Answer 18

part of genetic material has broken off, turned and attached itself upside down

Question 19

deletion

Answer 19

part of a chromosome is missing

Question 20

Insertion

Answer 20

part of a chromosome is removed from its usual place and inserted elsewhere

Question 21

translocation

Answer 21

part of a chromosome has been transferred to another chromosome

can lead to fused genes producing fused proteins

Question 22

two types of chromosomal translocation:

Answer 22

reciprocal - one part is changed for another

robertsonian - a whole chromosome is joined end to end with another

Question 23

ring chromosomes

Answer 23

ends of chromosomes fuse together, forming a ring

Question 24

why may ring chromosomes arise?

Answer 24

radiation

Question 25

What are mutagens?

Answer 25

physical or chemical agents that alter genetic material and therefore the chance of mutations.

Question 26

How do mutagens work?

Answer 26

strong ones can cause chromosomal instability leading to breakages or rearrangements

Question 27

examples of physical mutagens:

Answer 27

X rays UV radiation UV light (can promote formation of T and C bases)

Question 28

examples of chemical mutagens:

Answer 28

reactive oxygen species nitrous acid benzene